Video information recording method and video information reproducing apparatus

ABSTRACT

The amount of data stored in a video buffer ( 3 ) that temporarily stores multi-angle streams (A, B) is controlled from information giving the distance between the angle blocks (A —   1 , B —   1 , A —   2 , B —   2 , . . . ) of the multi-angle streams and an audio stream (C) on a recording medium ( 10 ). In multi-angle playback, in which multiple files are read simultaneously, this can shorten the time from when the user switches the angle until the image reproduced by a video display apparatus changes to the intended angle.

FIELD OF THE INVENTION

The present invention relates to a method of recording video informationon optical discs and other disc-shaped recording media and a videoreproducing apparatus for reproducing video information from therecording media.

BACKGROUND ART

As a method of reproducing two or more files that have been recorded onan optical disc while reading them in turn, a system that reads twofiles alternately and reproduces them by preparing a comparatively largebuffer memory, reading a sufficient part of one file into the buffermemory, then reading the other file, and repeating these operationsalternately has been proposed (in Patent Document 1, for example).

Patent Document 1: International Publication WO/2002/023896 DISCLOSUREOF THE INVENTION Problems to be Solved by the Invention

A general method of simultaneously reproducing a video data filerecorded on a disc and a data file, for example, an audio data file,placed in a position physically separate from the video data file on thedisc will now be described.

When two files are reproduced simultaneously, a general method is toprepare a sufficiently large buffer for each file, read a sufficientquantity of data into the buffer, and then resume reading the other filebefore the other file's buffer becomes empty. In order to enable allreproducing apparatus to reproduce without interruption, that is, toincrease compatibility between reproducing apparatuses, there arespecified standards for the physical positions of the two files, thefile reading rate (speed), the size of the buffer memory thattemporarily stores a file that has been read, etc. It will be assumedhere that the encoding rate of the video file is specified at 5 Mbps andthe maximum difference between the physical positions of the two filesis specified as one-half stroke or less. One-half stroke means one halfof the distance between the innermost track and the outermost track ofthe recording area on the disc. It is also assumed that the timerequired for the drive that reproduces the disc to seek one-half strokeis 1 sec.

A reproducing method that does not interrupt the decoding of video dataand audio data will now be described on the conditions given above.During the reading of the video data, when an excursion is made to readthe audio data, while seeking to the position of the audio data, readingthe audio data, and then returning to read the video data again,reproduction must be carried out by using the video data stored in thebuffer. If it takes 1 sec to read the audio data, then for a total of 3sec, the video data cannot be read and reproduction must proceed byusing the video data stored in the buffer. Therefore, before departingto read the audio data, it is necessary to have a minimum of 15 Mbits ofvideo data stored in the video buffer.

Since several seconds of video data are read into and held in the bufferas described above, a disadvantage arises when, for example, multi-anglecontent is reproduced. The multi-angle function generally used in DVDsetc. enables the user to choose arbitrarily from among images that wererecorded simultaneously from a plurality of camera angles. Multi-anglecontent is reproduced by selectively reading only the video data for aspecified angle, and when the user performs a switching operation,reading the video data for a different angle. Therefore, if 15 Mbits ofdata are stored in the buffer, when the data stream to be read isswitched, the data for the angle before the switchover continue to bedecoded and displayed until the data stored in the buffer have beenconsumed. More specifically, after the user gives an instruction toswitch angles, it may take 3 seconds or more until the angle is actuallyswitched, significantly impairing ease of operation. A method ofavoiding this problem is to read the data for all angles, but becausethis method requires a drive with a high-speed reading capability and alarge-capacity buffer memory, it is costly and unrealistic.

An object of the present invention, in order to solve the problemdescribed above, is to provide a disc recording method and a videoinformation reproducing apparatus that can switch the image angledisplayed by a video display apparatus in a short time after the userhas performed an angle switching operation, even when two or more filesare reproduced simultaneously.

Means of Solution of the Problems

In a method of recording on a disc-shaped recording medium permittingmulti-angle playback, the video information recording method of thepresent invention is a video information recording method that:

successively records angle blocks, each including one or two or moreGOPs of a video data stream for one angle, in a first recording area onthe recording medium; and

records a related stream, to be reproduced simultaneously with themulti-angle video data streams, in a second recording area on therecording medium;

and is characterized by

recording distance information indicating a distance on the recordingmedium between the part of the first recording area in which each angleblock is recorded and the corresponding part of the related stream inthe second recording area, to be reproduced simultaneously with theangle block.

EFFECT OF THE INVENTION

According to the present invention, when multi-angle content isreproduced, even if a plurality of files are read simultaneously andreproduced simultaneously, after the user has performed an angleswitching operation, the newly selected video data can be displayedpromptly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the syntax of an index information file ingeneral multi-angle playback.

FIG. 2 is a diagram illustrating the physical arrangement of streams foruse in multi-angle playback in general multi-angle content on a disc.

FIG. 3 is a diagram illustrating the structure of a video informationreproducing apparatus in an embodiment of the invention.

FIG. 4 is a diagram illustrating the physical arrangement of streams foruse in multi-angle playback and an audio stream read alternately withthose streams on a disc.

FIG. 5 is a diagram showing the syntax of an index information file in afirst embodiment.

FIGS. 6( a) and 6(b) are diagrams indicating variations in the amount ofdata in the video buffer 3 and the audio buffer 4 over time in theoperation in the first embodiment.

FIG. 7 is a diagram illustrating the physical arrangement of streams foruse in multi-angle playback and an audio stream read alternately withthose streams on a disc in a second embodiment of the invention.

FIG. 8 is a diagram showing the syntax of an index information file inthe second embodiment.

FIG. 9 is a diagram illustrating the structure of a video informationreproducing apparatus in a third embodiment of the invention.

FIG. 10 is a diagram illustrating the physical arrangement of right-eyestreams and left-eye streams in angle blocks on a disc in the thirdembodiment.

FIG. 11 is a diagram illustrating the physical arrangement of streamsfor use in multi-angle playback and audio streams read alternately withthose streams on a disc in the third embodiment.

FIG. 12 is a diagram showing the syntax of an index information file inthe third embodiment.

FIGS. 13( a) and 13(b) are diagrams indicating variations in the amountof data in the video buffers 3 and 13 and the audio buffer 4 over timein the operation in the third embodiment.

FIG. 14 is a diagram showing the syntax of an index information file inthe third embodiment.

EXPLANATION OF REFERENCE CHARACTERS

-   1 drive, 2 multiplexer, 3 video buffer, 4 audio buffer, 5 video    decoder, 6 audio decoder, 7 video display apparatus, 8 control unit,    13 video buffer, 14 video decoder

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will now be described with reference to theattached drawings.

The video information recording method and the video informationreproducing apparatus in the embodiments of the present invention carryout recording and reproducing operations on disc-shaped recording media:for example, general optical disc recording media such as DVD, CD,Blu-ray, HD-DVD, and other such recording media.

First Embodiment

First, the features of multi-angle data will be described. In the firstembodiment, for simplicity of description, an exemplary case with twoangles will be described. In order to facilitate angle switching, theseek time resulting from angle switching must be shortened. Accordingly,the two data are placed in physically close proximity and arerespectively divided into angle blocks, and the angle blocks in the twostreams are placed alternately to shorten the seek time.

An angle block is a minimum unit of data that are reproducedcontinuously; angle switching is performed at the head of an angleblock, not at a point partway through an angle block. Because video dataare generally encoded by use of MPEG-2 etc., video data can be decodedonly from an I-picture at the start of a GOP (Group of Pictures).Accordingly, in order to switch angles without interruption, angleswitching must be performed at the first picture of a GOP, and the GOPmust be a closed GOP. More specifically, the first data of an angleblock are the first picture of a GOP, and each angle block includes atleast one GOP. The Presentation Time Stamp (PTS) of the first video dataof the n-th angle block in each of a plurality of streams (for example,angle block An of stream A) and the PTS of the first video data of then-th angle block of each other stream (for example, angle block Bn ofstream B) indicate the same time. Because the audio data do not changewhen angles are switched, the n-th angle block of each stream includesthe same audio data. The streams that are used in angle switching havethe same number of angle blocks.

FIG. 1 gives the syntax of an index information file indicating therelationship between the time information of the first I-picture of aGOP in a stream and the physical position of the I-picture; there is onesuch file per stream file.

The index information file is stored as a separate file from the streamfiles including streams A and B on the disc. The video informationreproducing apparatus reads the index information files first and thenreads the stream files including streams A and B.

In the index information file, “Number_of_GOP” indicates the totalnumber of GOPs included in the stream file to be reproduced, and thefollowing “For” loop is repeated that number of times. The informationin the file is required for random access, I-picture search, and angleswitching. “GOP_id” indicates the ID number of a GOP in the stream, andis incremented from 0. “I_PTS” indicates the PTS time of the I-picture.“I_SCN” indicates the relative number of bytes from the first byte ofthe stream to the first byte of the first picture of the GOP. Thereproducing apparatus can learn the relationship between the reproducingtime of the first picture of the GOP and the position on the disc fromthe “I_PTS” and “I_SCN” information. “Angle_flag” indicates whether theGOP is at a point at which angles can be switched; a value of “1”signifies an angle switching point. The “Angle_flag” of the indexinformation indicating the head of an angle block is always “1”.

FIG. 2 is a diagram illustrating the arrangement in which the aboveangle blocks are stored on a recording medium 10. Stream A (the firststream), which is the stream for the first angle, and stream B (thesecond stream), which is the stream for the second angle, are stored ina first recording area 11. Video data and audio data are multiplexed ineach stream. The angle blocks A₁, A_2, A_3 . . . and B_1, B_2, B_3 . . .in streams A and B are placed alternately.

FIG. 3 is a diagram illustrating an entire video information reproducingapparatus according to the invention.

The video information reproducing apparatus shown in FIG. 3 has a drive1, a demultiplexer 2, a video buffer 3, an audio buffer 4, a videodecoder 5, an audio decoder 6, a video display apparatus 7, and acontrol unit 8.

The drive 1 reads video data and audio data from a recording medium 10.The demultiplexer 2 demultiplexes the video data and audio data thathave been read by the drive 1. The video buffer 3 temporarily stores thevideo data that have been read from the recording medium 10. The audiobuffer 4 temporarily stores the audio data that have been read from therecording medium 10.

The video decoder 5 reads the video data stored in the video buffer 3,decodes the video data, and supplies the decoded video data to the videodisplay apparatus 7. The audio decoder 6 reads the audio data stored inthe audio buffer 4, decodes the audio data, and supplies the decodedaudio data to the video display apparatus 7. The video display apparatus7 displays video data according to the decoded video data received fromthe video decoder 5, and outputs sound according to the decoded audiodata received from the audio decoder 6.

The control unit 8 controls the operations of the elements from thedrive 1 to the video display apparatus 7 described above and includes,for example, at least one CPU and a program memory, so that part or allof the control unit 8 is implemented by software, that is, by theoperation of the CPU according to the program stored in the programmemory.

Stream A recorded on the recording medium 10 is read by the drive 1, anddemultiplexed into video data and audio data by the demultiplexer 2. Thedemultiplexed video data are temporarily stored in the video buffer 3.

The video data of each angle block of stream A are stored successivelyin the video buffer 3. The video data are transferred from the videobuffer 3 to the video decoder 5 and decoded in the video decoder 5 intoa video signal that is output to the video display apparatus 7, which isa TV or the like. The demultiplexed audio data are temporarily stored inthe audio buffer 4 and decoded in the audio decoder 6 into a soundsignal that is output to the video display apparatus 7 (e.g., the TV).

When stream A is reproduced continuously, the angle blocks of stream Bare skipped and the angle blocks of stream A are read and sent to thedemultiplexer 2.

If the user performs an angle switching operation during the reproducingof stream A, the control unit 8 issues a command to the drive 1 to readstream B. If the angle block of stream A that is currently being read isangle block A_n, the switchover to stream B starts at angle blockB_(n+1).

The control unit 8 identifies the starting position of angle blockB_(n+1) in stream B from the index information file stored in thecontrol unit 8, which has been read in advance of the reading of streamsA and B, and directs the drive 1 to start reading from angle blockB_(n+1). Accordingly, the data of angle block B_(n+1) are storedfollowing the data of angle block A_n in the video buffer 3 and theaudio buffer 4, and when the video data of angle block B_(n+1) aredecoded in the video decoder 5 and output as the video signal, the usercan see that the angle has been switched.

The angle switching operation described above involves only the streams(here, streams A and B) necessary for multi-angle playback. However,depending on the content that is being reproduced, reproduction may haveto be simultaneous with the reproduction of a file other than the filesnecessary for multi-angle playback. For example, for some content theaudio data and video data are reproduced asynchronously. In a slide showdisplay with music played in the background, for example, although thevideo is switched to the next slide by the user, sound reproductioncontinues independently of the switching of the video. In situationslike this, pictures and sound are reproduced asynchronously. Becausevideo and audio cannot be reproduced from one multiplexed stream in suchsituations, a different stream must be provided for the audio. Insituations like this, reproduction must be performed while alternatelyreading the multi-angle video stream and the stream used for audioreproduction.

Next, the multi-angle playback operation will be described in a contextin which reproduction is performed while alternately reading amulti-angle video stream and an asynchronously reproduced audio stream.

FIG. 4 is a diagram illustrating the arrangement on a recording medium10 of streams A and B, which are used for multi-angle playback, andstream C, which is read simultaneously. The arrangement of streams A andB is the same as described with reference to FIG. 2. Streams A and B maybe referred to as the ‘main streams’ and stream C as a ‘related stream’.

Streams A and B include only video data. Stream C is situated on a tracka certain distance X mm from the track on which streams A and B arerecorded. Stream C includes only audio data.

Thus, streams A and B are placed in the first recording area 11 on therecording medium 10, and stream C is placed in a second recording area12 on the recording medium 10.

The video buffer 3 temporarily stores the video data (the blocks ofstream A or B) that have been read from the first recording area 11, andthe audio buffer 4 temporarily stores audio data (the corresponding partof stream C) that have been read from the second recording area 12 andmust be reproduced simultaneously with the video data stored in thevideo buffer 3, or simultaneously with video data reproduced immediatelybefore or after the video data stored in the video buffer 3. Stream C isalso referred to as a related stream that must be reproducedsimultaneously with streams A and B. Since writing and reading areperformed alternately in the video buffer 3 and audio buffer 4,corresponding audio data are not always stored in the audio buffer 4 forall video data stored in the video buffer 3. In other words, the audiobuffer 4 temporarily stores audio data (the corresponding part of streamC) that must be reproduced simultaneously not only with the video datastored in the video buffer 3 but also with video data to be reproducedimmediately before or after the video data stored in the video buffer 3,and the video buffer 3 temporarily stores video data that must bereproduced simultaneously not only with the audio data stored in theaudio buffer 4 but also with audio data to be reproduced immediatelybefore or after the audio data stored in the audio buffer 4.

FIG. 5 is a diagram showing the syntax of an index information file of avideo stream used for multi-angle playback. In the index informationfile in FIG. 5, the syntax differs from the syntax in FIG. 1 by theaddition of “file_distance” information. The “file_distance” informationindicates the physical distance between stream A or B and the stream Cthat is read simultaneously (concurrently).

This index information file is stored as a separate file from the videostreams (streams A and B) and audio stream (stream C) on the disc. Thevideo information reproducing apparatus reads the index information filefirst and then reads the audio and video streams, as described above.

It is assumed here that the encoding bit rate (accordingly, the readingrate from the video buffer 3) of streams A and B is 5 Mbps, the encodingbit rate (accordingly, the reading rate from the audio buffer 4) ofstream C is 0.5 Mbps, the data reading rate (speed) of the drive 1 is 10Mbps, and the physical distance between stream A or B and stream C is 10mm. The relationship between the time required for the drive 1 toexecute a seek (the seek time) and the seek distance is as shown inTable 1; the data shown in Table 1 are stored in, for example, thecontrol unit 8. As the data shown in Table 1, specific values may bestored for a particular video information reproducing apparatus (or avideo information reproducing apparatus of particular type), or valuescorresponding to the minimum value of a seek speed range required in aspecification may be stored.

TABLE 1 Seek distance Seek time  0-1 mm  50 msec  1-10 mm 300 msec 10-20mm 500 msec 20-30 mm 750 msec 30-40 mm 1000 msec  40-50 mm 1250 msec 

The “file_distance” in the index information file is now set at 10 mm.From the seek speed table (Table 1) it can be seen that when the“file_distance” is 10 mm, the required seek time is 300 msec. If ittakes 400 msec to read stream C (reading time), it takes a total of300+400+300=1000 msec from seeking to stream C until returning to readstream A again. Because the amount of data stored in the video buffer 3that is consumed (read) during 1000 msec is

1 sec×5 Mbps=5 Mbits,

before starting to seek to stream C, it is necessary to have 5 Mbits ofdata stored in the video buffer 3. In actual practice, a little extramargin is necessary, so 6 Mbits of data are stored, allowing about anextra 1 Mbit.

Seeking to stream C starts when the amount of data in the audio buffer 4falls to a prescribed value. More specifically, the time at which theamount of data in the audio buffer 4 would become zero (or a quantitygreater than zero by a slight margin) if reading from the audio buffer 4continued (without writing in the audio buffer) is predicted from theamount of data in the audio buffer 4 and the encoding rate (the readingrate from the audio buffer 4), and seeking starts at a time precedingthe predicted time by just the required seek time. In the firstembodiment, the ‘slight margin’ mentioned above is 1.2 Mbits, andbecause the encoding rate is 0.5 Mbps and the seek time is 0.3 seconds,seeking starts when the amount of data in the audio buffer 4 becomes

1.2 Mbits+0.3×0.5=1.35 Mbits.

FIGS. 6( a) and 6(b) are diagrams indicating variations in the amount ofdata in the video buffer 3 and the audio buffer 4 over time.

At time T0, when it is detected that the amount of data in the audiobuffer 4 has reached (fallen to) the prescribed value of 1.35 Mbits,seeking to stream C starts. The amount of data in the video buffer 3 isthen 6 Mbits. Although the control unit 8 directs the drive 1 to seek tostream C at time T0 and seeking starts then, because video is reproducedduring the seek, consuming the data stored in the video buffer 3, thedata in the video buffer 3 continue to decrease at the encoding bit rateof 5 Mbps, and the data in the audio buffer 4 continue to decrease atthe rate of 0.5 Mbps. At time T1, 300 msec later, seeking is completed,and the reading of stream C starts.

At time T1, the amount of data in the audio buffer 4 is 1.2 Mbits. Ifthe audio encoding rate is 0.5 Mbps and the data reading rate of thedrive 1 is 10 Mbps as described above, then at time T2, 400 msec aftertime T1, because of the 400 msec of reading, the amount of data in theaudio buffer 4 is

(10−0.5)Mbps*0.4 sec+1.2 Mbits=5.0 Mbits.

Because the audio encoding rate is 0.5 Mbps, if the reading of stream Ccan recommence within a maximum of 10 seconds from time T2, sound can bereproduced without interruption. The drive 1 starts another seek at timeT2, and starts the reading of stream A at time T3, 300 msec after timeT2.

Because the time from time T0 to time T3 is 1 sec, at time T3, theamount of data in the video buffer 3 is

6 Mbits−5.0 Mbps*1.0 sec=1.0 Mbit.

Next, the drive 1 reads stream A until the data stored in the videobuffer 3 reaches 6 Mbits at time T4. After time T4, the control unit 8controls the video buffer 3 by repeatedly reading and pausing so as tokeep at least 6 Mbits of data in the video buffer 3. Streams A and C areread alternately and reproduced thereafter by repetitions of similaroperations.

The quantity ‘6 Mbits’ is obtained by adding a margin (1 Mbit) to theamount of data (5 Mbits) read from the video buffer 3 in the total (1sec) of the time (0.3 sec) taken to seek from the first recording area11 in which stream A is stored to the second recording area 12 in whichstream C is stored, the time (0.4 sec) required for reading stream C inthe second recording area 12 and writing into the audio buffer 4 untilthe amount of data in the audio buffer 14 has increased to a prescribedquantity (e.g., 5 Mbits), and the time (0.3 sec) taken to seek from thesecond recording area 12 to the first recording area 11, as describedabove; the control unit 8 estimates the required seek time withreference to Table 1, according to the information indicating thedistance from the first recording area 11 to the second recording area12.

As described above, the control unit 8 controls and varies the amount(size) of data that must be stored in the video buffer 3 according tothe information indicating the distance from the first recording area 11to the second recording area 12, the writing rate in the audio buffer 4,the reading rate from the audio buffer 4, and the amount of data (5Mbits) that should be stored in the audio buffer 4 before seeking to thefirst recording area 11 from the second recording area 12 starts.

At time T5, a command to switch angles is issued by an operation by theuser, and seeking to stream B starts. At time T5, the control unit 8issues a command to seek to the head of the data in the angle block ofstream B corresponding to the data of the next angle block (the angleblock to be reproduced next) after the data of the newest angle blockcurrently stored in the video buffer 3. If, for example, the n-th angleblock An of stream A is being reproduced, the (n+1)-th angle blockB(n+1) of stream B is the angle block to be reproduced next. Because thestreams used for multi-angle playback are placed in physically highlyclose proximity as described above, seeking from stream A to stream Bcan be completed in a very short time: for example, 50 msec as shown inTable 1.

A similar short seek time is necessary when the reading of the nextangle block (An+1) starts after the reading of an angle block (forexample, angle block An) from the same stream (for example, stream A).

The reading of stream B starts at time T6, 50 msec after time T5.Because the amount of data of stream A remaining in the video buffer 3is approximately 6 Mbits at the time T6 at which the reading of stream Bstarts, the time until the video angle that is reproduced in the videodisplay apparatus 7 is actually switched (the time until thereproduction of stream B starts) is approximately 1.2 seconds. Streams Band C are read alternately and reproduced thereafter (this operation isexactly the same as the operation when streams A and C are readalternately and reproduced).

As described above, in the first embodiment, the ‘file_distance’ is usedto vary the amount of data stored in the video buffer 3 according to thedistance between the streams used for multi-angle playback and therelated audio stream (that is, the stream that must be readalternately).

In a conventional method that does not use this information, since thereproducing apparatus cannot learn the distance between two files, theamount of data stored in the video buffer 3 must always be set on theassumption of the maximum distance between streams A and C, even if theactual distance between the two streams is short. If, for example, thespecified maximum distance between two files is 40 mm, assuming that thedistance has the maximum value of 40 mm regardless of the distancebetween the streams being actually read means that at least 2.4 secondsof data must be stored in the video buffer. Therefore, when angles areswitched, a minimum of 2.4 seconds is necessary until the video anglereproduced by the video display apparatus 7 is actually switched,regardless of the distance between the two files.

When the ‘file_distance’ is used as in the first embodiment, thereproducing apparatus can always keep the amount of data in the videobuffer at the minimum required by the distance between two files.Accordingly, a reproducing apparatus can be provided that can switchangles in a shorter time, after the user has switched the angle, thanwhen the ‘file_distance’ is not used.

Second Embodiment

Although the angle switching time can be shortened by using the‘file_distance’ in the first embodiment, an insufficient shorteningeffect may be obtained when the streams used for multi-angle playbackare very long files. FIG. 7 is a diagram illustrating a data arrangementon the recording medium 10 in which streams A and B in FIG. 4 are verylong. In this situation, although the distance between the end 11 e ofstream A and stream C is 10 mm, the distance between the beginning 11 bof stream A and stream C is 40 mm. In situations like this, because thelong distance of 40 mm is set as the ‘file_distance’, when the part ofstream A near the end 11 e is reproduced, the size of the data stored inthe video buffer 3 is greater than necessary. In this example, although1.0 second of data would be satisfactory at the end lie, 2.4 seconds ofdata must be stored, the same as when the beginning 11 b is reproduced.Accordingly, when the angle is switched near the end, the time requireduntil the angle is actually switched is longer than necessary.

FIG. 8 shows an index information file obtained by modifying the indexinformation in FIG. 5 in order to solve this type of problem. Thedifference between the index information files in FIGS. 8 and 5 is thatthe “file_distance” information for each angle block is placed in theangle block: for example, in the GOP loop of the angle block (the“file_distance” of each GOP is specified in the “for” loop). The correctdistance from each angle block of a stream to stream C can be learned byproviding “file_distance” information for each GOP as described above.Because the “file_distance” value corresponding to an angle block nearthe end of the stream is 10 mm in the example described above, the datasize stored in the video buffer 3 can be controlled to 1.0 second ofdata.

If the index information file is modified as described above, areproducing apparatus can be provided that can always switch angles inthe minimum necessary time because it can tell the shortest distancefrom any point on the stream being reproduced.

When not only streams A and B but also stream C is very long,information giving the distance between each part of stream A or B andthe part of stream C that must be reproduced simultaneously with thatpart may be stored in that part of stream A or B.

The above-described distance information for each angle block may bestored in the angle block, or in a management area on the recordingmedium 10.

Third Embodiment

The method described in the first and second embodiments uses the“file_distance” information to reproduce a multi-angle stream andanother stream simultaneously; the third embodiment will describe theapplication of the “file_distance” in exactly the same way when themulti-angle stream provides a three-dimensional picture.

FIG. 9 is an overall depiction of a video information reproducingapparatus that displays three-dimensional streams. This videoinformation reproducing apparatus differs from the video informationreproducing apparatus in FIG. 3 by the addition of a video buffer 13 anda video decoder 14. Video buffer 13 and video decoder 14 are exactlyidentical to video buffer 3 and video decoder 5. The data read by thedrive 1 are demultiplexed into right-eye video data, left-eye videodata, and audio data by the demultiplexer 2. The right-eye video dataare temporarily stored in video buffer 13 and decoded by video decoder14 into a video signal that is output to the video display apparatus 7.The left-eye video data are temporarily stored in video buffer 3 anddecoded by video decoder 5 into a video signal that is output to thevideo display apparatus 7.

FIG. 10 is a diagram illustrating angle blocks A1 and B1 in FIG. 2 indetail. The left-eye image data L1 to L3 of angle block A1 and theright-eye image data R1 to R3 are divided into sizes such as not tounderflow or overflow video buffer 3 and video buffer 13, and are placedalternately. The data are demultiplexed into left-eye image data andright-eye image data by the demultiplexer 2; the demultiplexed left-eyeimage data are sent to the video buffer 3; the demultiplexed right-eyeimage data are sent to the video buffer 13. The angle block constraintsare the same as in the first embodiment; a description will be omitted.

When a multiplexed three-dimensional stream is output to a TV orreproducing apparatus that does not support three-dimensional video, itbecomes necessary to decode just one part of the video data andreproduce it as two-dimensional video. Accordingly, depending on thecontent, the streams read simultaneously when two-dimensional video isdisplayed may differ from the streams read simultaneously whenthree-dimensional video is displayed. The stream reproducedsimultaneously, e.g., the audio data stream, may then also differ,depending on the video. Here, when either right-eye video data orleft-eye video data are decoded as two-dimensional video, the streamread simultaneously will be stream C, and when the video data for botheyes are decoded, the stream read will be stream D. FIG. 11 is a diagramillustrating the physical positional relationships on the disc betweenthe three-dimensional angle blocks, an area 12 c in which stream C isplaced, and an area 12 d in which stream D is placed.

FIG. 12 gives the syntax of an index information file obtained by theaddition of “file_distance_3D”, indicating the distance to stream D, tothe syntax of the index information file in FIG. 5. The distance betweenthe angle blocks and stream C is given by “file_distance” and thedistance between the angle blocks and stream D is given by“file_distance_3D”. When both the right-eye and left-eye streams aredecoded, the reproducing apparatus controls video buffer 3 and videobuffer 13 with reference to the “file_distance_3D” value. When one ofthe right-eye and left-eye streams is decoded as two-dimensional video,the reproducing apparatus controls video buffer 3 and video buffer 13with reference to the “file_distance” value.

Exemplary variations in the amount of data in the video buffers 3 and 13and audio buffer 4 over time when such control is performed are shown inFIGS. 13( a) and 13(b). At time T14, the data stored in the video buffer13 have reached 6 Mbits in FIG. 13( a).

Even when the multi-angle area 11 is used for storing three-dimensionalvideo data, one stream is read simultaneously when the data arereproduced as three-dimensional video, and another stream is readsimultaneously when the data are reproduced as two-dimensional video, ifthe index information file is modified as described above, a reproducingapparatus can be provided that can switch angles in a short time.

If “file_distance 3D” is placed in the “for” loop as shown in FIG. 14,as in the second embodiment, even when a three-dimensional stream thatis used for multi-angle playback is a very long file, a reproducingapparatus can be provided that can always switch angles in the minimumnecessary time.

When not only streams A and B but also streams C and D are very long,information giving the distance between each part of stream A or B andthe part of stream C or D that must be reproduced simultaneously withthat part may be stored in that part of stream A or B.

The above-described distance information for each angle block may bestored in the angle block, or in a management area on the recordingmedium 10.

Although a multi-angle area is reproduced in the first, second, andthird embodiments described above, when one video is multiplexed withplural audio in one stream (the main stream) and the audio multiplexedin the main stream is switched while simultaneously reading a streamrecorded in another area, the audio can be switched quickly if the“file_distance” information is used. The “file_distance” information isalso applicable not only to the switching of audio in the main streambut also to, for example, the switching of graphics for displayingsubtitles or, for example, the switching of optional video forperforming a picture-in-picture display, or whenever there are aplurality of switchable streams multiplexed in one area.

1. In a method of recording on a disc-shaped recording medium permittingstream switching such as multi-angle playback, audio switching, andsubtitle switching, a video information recording method that: records astream in which a video stream, an audio stream, and a subtitle streamare multiplexed in a first recording area on the recording medium; andrecords a related stream, to be reproduced simultaneously with thestream recorded in the first recording area, in a second recording areaon the recording medium; characterized by recording distance informationindicating a distance on the recording medium between the streamrecorded in the first recording area and the corresponding part of therelated stream in the second recording area, to be reproducedsimultaneously with the stream recorded in the first recording area. 2.The video recording method of claim 1, wherein the distance informationis recorded in a management area on the recording medium.
 3. The videorecording method of claim 1, wherein the distance information indicatingthe distance between the stream recorded in the first recording area andthe corresponding part of the related stream, to be reproducedsimultaneously with said stream, is recorded in an index informationfile giving GOP starting position information.
 4. The video recordingmethod of claim 1, wherein the distance information indicating thedistance between the stream recorded in the first recording area and thecorresponding part of the related stream, to be reproducedsimultaneously with said stream, is recorded in the stream recorded inthe first recording area.
 5. A video information reproducing apparatusfor reproducing a recording medium recorded by the method of claim 1,comprising: a first buffer memory for temporarily storing the streamread from the first area; a second buffer memory for temporarily storingdata of the corresponding part of the related stream read from thesecond area, to be reproduced simultaneously with the stream stored inthe first buffer memory; and a control unit for varying a size of datato be stored in the first buffer memory according to the distanceinformation indicating the distance between the part of the firstrecording area in which the stream being reproduced is recorded and thepart of the second recording area in which the corresponding part of therelated stream, to be reproduced simultaneously with said stream, isrecorded, when the first recording area and the second recording areaare read alternately, stored in the first and second buffer memories,read from the first and second buffer memories, and reproduced.
 6. In amethod of recording on a disc-shaped recording medium permitting streamswitching such as multi-angle playback, audio switching, and subtitleswitching, a video information recording method that: records a streamin which a video stream, an audio stream, and a subtitle stream aremultiplexed in a first recording area on the recording medium; andrecords related streams, to be reproduced simultaneously with the streamrecorded in the first recording area, in a second recording area and athird recording area on the recording medium; characterized byrecording: distance information indicating a distance on the recordingmedium between the stream recorded in the first recording area and thecorresponding part of the related stream in the second recording area,to be reproduced simultaneously with the stream recorded in the firstrecording area; and distance information indicating a distance on therecording medium between the stream recorded in the first recording areaand the corresponding part of the related stream in the third recordingarea, to be reproduced simultaneously with the stream recorded in thefirst recording area.
 7. The video recording method of claim 6, whereinthe distance information is recorded in a management area on therecording medium.
 8. The video recording method of claim 6, wherein thedistance information indicating the distance between the stream recordedin the first recording area and the corresponding part of the relatedstream to be reproduced simultaneously with said stream is recorded inan index information file giving GOP starting position information. 9.The video recording method of claim 6, wherein the distance informationindicating the distance between the stream recorded in the firstrecording area and the corresponding part of the related stream to bereproduced simultaneously with said stream is recorded in the streamrecorded in the first recording area.
 10. A video informationreproducing apparatus that reproduces a recording medium recorded by themethod of claim 6, comprising: a first buffer memory for temporarilystoring a right-eye stream read from the first area and a second buffermemory for temporarily storing a left-eye stream; a third buffer memoryfor temporarily storing data of the corresponding part of the relatedstream read from the second area or the third area, to be reproducedsimultaneously with the streams stored in the first and second buffermemories; and a control unit for varying a size of data to be stored inthe first and second buffer memories according to the distanceinformation indicating the distance between the stream recorded in thefirst recording area and the corresponding part of the related streamrecorded in the second recording area or the third recording area, to bereproduced simultaneously with said stream, when the first recordingarea and the second recording area or the third recording area are readalternately, stored in the first, second, and third buffer memories,read from the first, second, and third buffer memories, and reproduced.11.-15. (canceled)